1. Field of the Invention
The present invention relates generally to chair construction and more particularly, to an ergonomically designed chair of the type primarily used in offices and having a construction which affords improved support for both the pelvic region and back of the chair occupant.
2. Description of the Prior Art
Many chairs of common design having a horizontal seat member and vertical back member do not provide support for the shoulder blades, the lumbar region of the spine and the pelvic region of the chair user. When in a standing position, the weight of a person's torso is supported by the hip bones and thus the shoulder muscles, the back muscles in the lumbar region and the muscles in the pelvic region have minimal load applied to them. However, in a seated position, as the thigh bones move upwardly, the pelvis of the chair user shifts posteriorly requiring the use of muscles to support the pelvic region, the lumbar region and shoulder blades. A typical chair has a back support member usually positioned above the seat and adapted to provide some support for the small of the user's back. However, the shoulder blades and pelvic region are usually unsupported, and after an extended period of time this can result in fatigue of the user's muscles thereby causing discomfort and pain.
In order to provide better back support of a chair user, it is known in the art to position a back pillow only slightly above the seat of the chair such that the pillow projects convexly forward over the rear seat area at the elevation of the ilia and sacrum with the person's back substantially unsupported in the lumbar region. Such a chair is disclosed, for example, in U.S. Pat. No. 4,489,982 issued to Morrow. As disclosed therein, this chair has the capability of maintaining the pelvis of the user at a sufficient sacral base angle that substantially the entire weight of the upper portion of the body of the user is supported by the seat of the chair.
However, a disadvantage of the foregoing chair is that the shoulders and lumbar region of the user are completely unsupported, requiring the user to maintain continuously an erect posture while seated. Should the user shift position, such as after an extended period of sitting, the support provided by the pillow can be completely ineffectual in maintaining the back of the user erect, causing arching of the spine and resulting dependence on back muscles to support the user while seated. Consequent muscle fatigue and associated pain thereby manifests itself particularly when the user is seated in the chair over long periods of time.
Accordingly, it is desirable to provide an improved chair, of the type used in an office setting for example, which provides support for the ilia and sacrum of the user while at the same time supporting the user's shoulder blades. It is further desirable to provide such a chair with the ability to allow for independent support of each shoulder blade as the user's torso rotates while seated in the chair. Still further, it is desirable to provide such a chair having a seat member which separately supports each leg of the user while allowing the legs to assume different vertical positions relative to one another. Further, it is desirable to provide such a chair with a construction involving relatively few components so that economies in manufacturing the chair can be realized.